The longterm objectives of these studies are to establish spontaneous feline hyperfunctional adenomatous goiter (toxic nodular goiter) as a model for human benign thyroid tumors, and to probe for molecular genetic abnormalities associated with the changeover from normal to adenomatous growth with maintained differentiated function. The proposed studies focus upon the factors controlling the normal cell cycle of the feline adenomatous thyrocyte cell lines. Particular attention will be paid to possible alterations in oncogene and anti-oncogene structure and expression. In order to acquire the necessary techniques to accomplish this longterm goal, this proposal outlines pilot work which will allow the principal investigator to incorporate molecular genetic techniques into ongoing and future research projects in thyroidology. In experiments involving the feline adenomatous thyrocyte cell lines PETCAT-l,-2,-3,-4, and ROMCAT-1, this proposal has the following specific aims: 1. For the visiting researcher to become familiar with the molecular genetic techniques of RNA and DNA extraction and purification, nucleic acid electrophoresis, dot blot assays, Northern and Southern blotting and hybridization techniques, and to learn about application of molecular genetic techniques to the study of cell cycle events. 2. To evaluate alterations in DNA structure and basal mRNA expression of known proto-oncogenes, transcription factors, tumor suppression factors, and signal transduction factors. 3. To study mRNA expression kinetics of growth-related genetic factors and compare them with the expression of factors associated with thyrocyte differentiation under conditions stimulatory for growth.